Traditional, so-called rumble strips have been in use for many years. These are often placed in three or four groups of raised, parallel bars across one lane of traffic, perpendicular to the direction of travel in advance of stop signs or traffic lights as an alert to drivers. The tires of a vehicle passing over a rumble strip make a staccato buzz-saw-like sound, alerting a driver to an upcoming stop sign or traffic light, as in FIG. 2. In like manner, narrow rumble strips incorporated into the shoulder of a paved road will alert a dozing driver who may have inadvertently drifted onto a road's shoulder, as in FIG. 3, before the vehicle leaves the road entirely.
Musical rumble strips have been placed as a novelty or entertainment on roadways. In this usage, the spacing between bars is varied, so that when a vehicle travels over the strips at a steady speed, a few bars of a recognizable tune are reproduced, such as a college fight song, a national anthem or a current pop tune.
More recently, some automakers have incorporated rumble-strip detection systems into certain models of their automobiles, or have discussed doing so. One such system detects road-shoulder rumble strip will activate an electromechanical steering mechanism to automatically steer a car away from the shoulder and back onto the road. In a similar manner, passing over lane-width rumble strips as in FIG. 2 could activate an automatic braking system if, according to the system's calculations, the vehicle's driver and was not applying braking in a degree sufficient to manage a timely full stop at an upcoming stop sign, railroad crossing, intersection or other potential hazard.
All of these prior-art systems utilize analog techniques, similar to the 45- and 33-1/3-RPM/LP vinyl records of an earlier era. Pitch may be altered by adjusting the spacing between the individual rumble bars or vehicle speed. A vehicle-on-board system that has a speed sensor input can compensate for speed and calculate a bar spacing value. Different bar spacings may signal different events, such as leaving the left side of a road, leaving the right side of a road, or approaching a stop sign or traffic light. The number of different events that can be encoded in such a manner is quite limited.
An object of the present invention is to greatly expand the capabilities and function of rumble strips by incorporating digital techniques into their design. Another object of the present invention is to advance detection means, methods and apparatuses, achieving ends that are not achievable using conventional analog rumble strips.
Yet another object of the present invention is to detect and process the noise generated by one or more wheeled vehicles traveling over a road or other navigable surface wherein the surface has not been prepared or modified in any way, and to measure and distinguish certain parameters of each of those one or more vehicles individually by means of cross correlation between vehicle-generated noise received at multiple non-collocated transducers and applying digital signal processing techniques to perform any or all of time and pitch shifting, environmental-factors correction, amplitude adjustments and other adjustments to the multiple inputs from multiple sound and vibration transducers. The certain parameters include but are not limited to vehicle location, speed, direction, acceleration, deceleration and collisions between vehicles, or collisions between vehicles and fixed obstacles or terrain features.